Mobile telecommunications networks enable users of User Equipment (UE) to communicate with other such users via one of a number of base stations (eNodeB, eNB) and a core network 7. Each base station defines a number of cells of the network. In an active state a UE is registered with the network and has an RRC (Radio Resource Control) with a base station so that the network knows which cell the UE belongs to and can transmit data to and receive data from the UE. In LTE, in the Active state, the Handover procedure allows UEs to have service continuity while moving within the Intra LTE system (Intra and Inter Frequency) and towards other RATS (Radio Access Technologies). A UE at or near a border region between cells may move back and forth (“ping pong”) between cells and may as a consequence generate an excessive number of requests for reconnection to different base stations.
A UE also has a power conservation or idle state in which, typically, the UE is not transmitting or receiving data and no context about the UE is stored by the base station. In the idle state the location of the UE is known only (to the MME (Mobility Management Entity) in 3GPP) at the granularity of a Tracking Area (TA) comprising a cluster or group of base station cells.
When in the idle state, a UE selects and reselects cells according to the parameters broadcasted in the BCH (Broadcast Channel) and the base station is not aware of the cell selections/reselections made by the UE.
A wrong setting of the cell selection/reselection parameters may cause the UE to ping pong between the cells which may be harmful in terms of both signaling, processing and resource utilization.
For example, if the cell selection/reselection parameters are not properly set, then a Handover procedure may be performed as soon as the UE enters the Active state. A Tracking Area Update may also be performed if the UE is at Tracking Area border and the new Tracking Area is not in the list of TAs the UE is registered with.
Furthermore, ping-pong in idle state or mode may cause:                Paging messages to be lost during cell reselections, especially for inter freq/inter-RAT cell selection/reselection        Higher battery consumption in the UE because of repeated inter-freq/inter-RAT measurements        Service interruption if the ping-pang results in a cell selection procedure being performed.        